1. Field of the Invention
The present invention relates to a radio selective call receiver which is designed to receive an interleaved radio selective calling signal, and a receiving method thereof.
2. Description of the Related Art
In general, a battery-powered radio selective call receiver operates according to a battery saving scheme. More specifically, it Is determined whether a received selective calling signal is addressed to the receiver itself by conducting bit comparison between the received address information and the stored address information of its own. If the received selective calling signal is not addressed to its own station, the power supply to a radio receiving system is suspended. On the other hand, when the received selective calling signal is addressed to the receiver itself, then the power supply to the radio receiving system is continued and desired receiving operation is conducted.
There has been proposed a selective call receiver in Japanese Patent Application Laid-Open No. 60-182232. which shorten an unnecessary operation time to prolong the life of a battery. More specifically, the received address information is compared bit by bit to the stored address information of its own. At the time when the number of error bits exceeds a predetermined value, the radio receiving system is powered off to stop the receiving operation, resulting in reduced power consumption.
On the other hand, in the recent years. such a scheme that a plurality of data streams are interleaved in bits has been adopted. In the interleaving scheme, one block is formed of a plurality of words, and the bits of each word are interspersed in one block in a predetermined fashion. For example, four stings of 32-bit data: A1-A32, B-B32, C1-C32, and D1-D32 are interleaved to produce a sequence of A1, B1, C1, D1, A2, B2, C2, D2, A3, B3, C3, D3, . . . , A32, B32, C32, and D32. Such an interleaving scheme has features of high noise immunity and easy error correction.
In the interleaving scheme, since the bits of each word are interspersed in one block, all bits of address information are not complete unless all data of one block have been received. In a radio selective call receiver in a system adopting the interleaving scheme, therefore, at the time when all data of one block has been received, it is determined whether the radio selective calling signal is addressed to the receiver itself.
Therefore, it is necessary to receive all data of one block even when it is apparent that the received selective calling signal is not addressed to the receiver itself, resulting in useless operation and wasteful power consumption. From the viewpoint of prolonging the battery life, it is in need of improvement.
An object of the present invention is to provide an apparatus and method for receiving an interleaved selective calling signal, which can achieve reduced power consumption.
According to the present invention, in an apparatus for receiving an interleaved selective calling signal including a block of interleaved address data of a plurality of addresses each having a predetermined bit length, an address storage stores a predetermined address which has been assigned to the apparatus and a radio system receives the interleaved selective calling signal to produce interleaved reception data. The apparatus further includes a converter for converting the interleaved address data to address data for each of the addresses and a timing detector for detecting predetermined decision timing based on the interleaved address data, wherein the predetermined decision timing is set at a desired position within the block of the interleaved address data. An interim comparator is provided to compare partial address data for each of the addresses with a counterpart of the predetermined address stored in the address storage at the predetermined decision timing to produce a decision result for each of the addresses. A controller controls such that the radio system is selectively powered on and off at the predetermined decision timing based on decision results for the addresses.
Since an interim decision is performed at the predetermined decision timing within the block of the interleaved address data, it Is possible to determine whether the predetermined address is included in the received addresses at an earlier time before all the data of the block is received.
Further, when it is determined that the predetermined address is not included in the received addresses at the predetermined decision timing, the radio system is powered off, resulting in reduced power consumption and therefore improved battery life.